1. Field of the Invention
The present invention relates to trace detection of chemical and biological analyte, and in particular relates to the substrate and structure thereof.
2. Description of the Related Art
There are several poisonous chemical pollutants in the environment, and these pollutants have different detection standards, e.g. Amphetamine series (500 ppb), Cannabis metabolite (50 ppb), Paraquat (10 ppb), EPN (0.5 ppb), benzene (5.0 ppb), Clenbuterol (2.0 ppb), Malachite Green (2.0 ppb), nitrofuran (1.0 ppb), chloromycetin (0.3 ppb), and the likes. Only a few pollutants can be detected by immunization, most pollutants are quantitatively detected using mass spectrometry. Immunization is difficult to quantitatively analyze, and it needs further analysis such as mass spectrometry to improve detection reliability. However, mass spectrometry is expensive and time consuming, thereby limiting its timeliness and popularity. Therefore, those skilled in the art have spent significant effort to develop a highly sensitive, rapid, and low cost trace detection device to analyze biological and chemical analytes.
Raman scattering spectrum belongs to molecular vibration spectrum, and its full width half maximum (FWHM) width is far less than that of the fluorescence spectrum. As such, the Raman spectrum has the fingerprint specificity to express the molecular structure. However, the Raman scattering intensity is very weak. For example, about 106 to 108 incident photons make only 1 Raman scattering of inelastic collision, such that the trace detection based on the Raman scattering is difficult. The surface plasmon (in abbreviate SP) may resonant to form an ultra high electric field by the interaction of the metal nanostructure and the incident electromagnetic wave, thereby largely enhancing the Raman scattering. The described phenomenon is a so-called surface enhanced Raman scattering (in abbreviate SERS). It makes trace diction based on Raman scattering possible.
In U.S. Pat. No. 7,321,422 and U.S. Publication No. 2007/0285657, a periodic structure is formed on the substrate. However, the periodic structure has no continuous metal film thereon; it will limit its ability to adsorb significant amounts of magnetic molecules or positive/negative ions.
In U.S. Pat. No. 7,242,470, a nanostructure is formed on a substrate surface. However, this nanostructure is not periodic and its signal has low uniformity and reproducibility.
In U.S. Publication No. 2006/0119853, a commercial substrate is provided. The photon lattice structure 201, made of metal, a dielectric layer and a Bragg reflector 209 is adopted to enhance the Raman signals of the analyte 211 approaching the substrate. However, the surface structure of the silicon substrate is formed by physical etching or chemical etching, it is expensive and time costly.
Accordingly, a novel design of the detection device is still called for in order to solve the conventional problems.